Red-backed Vole; Myodes (photo by born1945 via Flickr)
Red-backed vole populations fluctuate with food supply. Their main food supplies are berries and tree seeds. Both of these crop yields are tied closely to weather conditions.
Voles reside in coniferous forests and hardly ever occupy grasslands. They have short lifespans reaching up to 1 year on average. During their lifetime, females can produce 5-6 offspring.
Boonstra, R., Krebs, C.J. Population dynamics of red-backed voles (Myodes) in North America. Oecologia 168, 601–620 (2012). https://doi.org/10.1007/s00442-011-2120-z